Hydrophilicity and surface energy of polyethylene modified by radiation grafting of acrylamide

Summary LDPE films were modified via direct γ-radiation grafting of acrylamide (AAm) from its 30% aqueous solution. Equilibrium swelling of the grafted samples in water, and a water/PAAm molar ratio in the swelled films were determined as a function of PAAm content. Contact angles formed by sessile drops of water or diiodomethane on the starting and modified LDPE were measured with following calculation of a surface energy in these samples. A gradual filling of LDPE surface with PAAm as well as changes in hydrophilic-hydrophobic properties of the composition during the grafting process was discussed. It has been found an essential increase in surface energy of the modified LDPE up to ∼15% of the grafted PAAm content with a further stabilization of the energy value. Received: 12 March 2001/Revised version: 26 June 2001/Accepted: 27 June 2001     

Debatable questions of surgical tactics in appendiceal infiltrates and periappendiceal abscess

The disease course in 68 patients with appendicular infiltrate (AI) and periappendicular abscess (PAA) is analysed. There were 42 men and 26 women at the age of 15-76 years. AI was detected in 12 patients, PAA-in 56 patients. In 39 patients diagnosis was made on the basis of clinical examination, laboratory tests and X-ray examination. Ultrasound examination was used in 19 cases. Conservative treatment appeared to be effective in 7 patients. The abscess developed in 4 patients. In 5 patients the diagnosis of AI was confirmed at the surgery. Opening and draining of the abscess was performed in 35 patients. The transabdominal opening of the abscess in combination with appendectomy was used in 19 patients. The median laparotomy, appendectomy and abdominal drainage were conducted in 2 patients with the break of the abscess into the abdominal cavity that led to the development of disseminated purulent peritonitis. The long-term results after the resolution of the infiltrate and opening of the abscess were analysed in 38 patients. The postoperative complications have developed in 29 patients, reoperation was performed in 7 of them. 2 of the 68 patients died after surgery. The total mortality rate was 2.9%, postoperative mortality-3.4%. Acute liver insufficiency (1) and intoxication (1) were the causes of death.     

High-voltage solar elements based on polycrystalline silicon

Problems connected with developing designs of high-voltage solar elements (SE) with vertical p- n transitions on the basis of polycrystalline silicon and also the results of analysis of new experimental data are considered. The photoelectric characteristics of SE with unilateral and bilateral illumination are presented. The prospects of using these SE in solar modules with parabolic-spherical and parabolic-cylindrical radiation concentrators are discussed.     

Hyperfine structure of magnetic-resonance electrical conductivity of doped polydiacetylene

Magnetic resonance with a hyperfine structure which can be detected from the electrical conductivity has been observed in iodine-doped polydiacetylene films. This resonance is attributable to transitions between Zeeman levels in the spin-dependent carrier transfer process in a system of localized paramagnetic centers. Pis’ma Zh. Tekh. Fiz. 25, 86–90 (December 12, 1999)     

A model of inventory control

A model of inventory control is considered. It is described by a semi-Markov random walk with a negative drift at an angle of 0 < α < 90°, with positive random jumps, a delay, an absorbing screen at zero, and a reflecting screen for a > 0 at an angle α. The Laplace transformation is found for the distribution of the first moment storehouse exhaustion, and the first and the second moments are explicitly obtained. Translated from Kibernetika i Sistemnyi Analiz, No. 4, pp. 50–59, July–August, 1999.